Interfaces now employ a variety of media-rich, social, and advanced decision-making components, including recommendation agents (RA) designed to assist users with their tasks. Social presence has been identified as a key consideration in website design to overcome the lack of warmth, social cues, and face-to-face interaction, but few studies have investigated the interface features that may increase social presence. Recent research on RAs has similarly acknowledged social presence as a key factor in the design of online RAs and in building trust in this technology, but there has been limited empirical work on the topic. In this study an experiment was conducted to explore how social technology cues, media capabilities, and individual differences influence social presence and trust in an RA. RA personality (extraversion), vividness (text, voice, and animation), and computer playfulness were found to influence social presence, with social presence serving in a mediating role and increasing user trust in the RA. Vividness also had a moderating effect on the relationship between RA extraversion and social presence such that increased levels of vividness strengthen this relationship.